1. Field of the Invention
This invention relates to a process for the complete combustion of hot gases of low calorific power, such as reducing smoke of rich gases and by-products of the carbonisation of coal, which gases are available under a pressure close to atmospheric pressure, which process uses at least one burner in a combustion chamber having means for introducing primary air and means for introducing secondary air. The invention also relates to a combustion chamber for carrying out the process.
2. Description of the Prior Art
The by-products of a coal pyrolysis installation, such as a rotary furnace, or a rotary hearth furnace, or a direct-fired furnace, are in a gaseous state and entrain fine solid products, such as carbon black, soot or coal dust, and condensible products such as tars or benzenes.
In conventional pyrolysis processes these by-products are generally subjected to sufficient cooling to achieve complete condensation, thereby making it possible to obtain in the carbonisation plant the negative pressure necessary for applying suction to the by-product with the aid of known means, such as extractor fans. If on the other hand it is desired to burn these by-products immediately at the outlet of the pyrolysis furnace, difficulties are encountered in transferring the gases from the pyrolysis furnace to the combustion furnace, in achieving complete combustion of the suspended particles, and finally in achieving the negative pressure necessary for the extraction of the gases because of the high temperature.
There are innumerable disappointing inventions relating to the collection of charging gases in coke oven plants. In particular, techniques aiming to burn the impurities lead to only very partial results, combustion being incomplete. Furthermore, equipment is periodically destroyed by explosions or local overheating.
A combustion chamber for the combustion of lean gases is known from U.S. Pat. No. 2,920,689. Air for combustion is supplied by a fan and divided into primary air and secondary air which are respectively supplied through valves to nozzles from which they pass out at high speed and with turbulence.
Furthermore, from French Pat. No. 2,193,178 a process is known for the extinction of stoichiometric combustion products by the injection of air with a view to limiting to 525.degree. C. the temperature of the gases discharged to the atmosphere. Moreover, an arrangement comprising two combustion chambers followed by an extinction chamber is known from French Pat. No. 2,065,890.
These arrangements have the major disadvantage of entailing the formation of a high-intensity turbulent flame, thereby making it necessary to use expensive refractory materials and to take special precautions against the risk of extinction and explosion, for example by maintaining a pilot flame. Moreover, stoichiometric proportions are difficult to maintain for gases whose calorific power may vary, as is frequently the case with numerous lean gases occuring as by-products of industrial processes, particularly when they contain crackable constituents at high temperature of high calorific power, such as carbon black and higher hydrocarbons.